Multiplicity among peculiar A stars - I. The Ap stars HD 8441 and HD 137909, and the Am stars HD 43478 and HD 96391P. North, J.-M. Carquillat, N. Ginestet, F. Carrier and S. UdryAstron. Astrophys. Suppl. Ser., 130 2 (1998) 223-232DOI: https://doi.org/10.1051/aas:1998365